The present invention relates to apparatus for converting blanks which consist of paper or the like into envelopes, e.g., into envelopes which can be used for shipment, storage or mailing of correspondence or other material.
Many presently known envelope making machines operate in such a way that a web of foldable material is caused to pass through a stamping or punching unit wherein a reciprocable punch removes discrete blanks from successive sections of the moving web. The blanks are thereupon stacked in a magazine and are withdrawn seriatim to advance through a folding apparatus which converts each blank into a discrete envelope. The folding apparatus further comprises suitable paster means for applying one or more layers of adhesive to one or more selected portions of each blank. It is also known to transport discrete blanks from the stamping or punching station directly to the folding apparatus.
In heretofore known folding apparatus, a blank moves lengthwise and is scored by suitable rollers which form fold lines between the two major panels as well as between a major panel and at least one lateral flap. The thus treated blank is transported past loop-shaped guides which consist of sheet metal or the like and fold the blank along the scored fold line between the two major panels. Thus, the blank is converted into a partly finished envelope wherein the two major panels overlie each other. The folding of one flap of the envelope is carried out by advancing the partially finished envelope into the range of an upsetting device which consists of sheet metal or the like and folds the one flap subsequent to movement of such flap along a paster which applies to one of its sides a layer of suitable adhesive. The upsetting device folds the one flap and presses it against the outer side of the adjacent major panel. The same procedure is followed for folding of the other flap or flaps of the blank, i.e., such other flap or flaps are coated with adhesive and each adhesive-coated flap is moved past a discrete upsetting device which folds the respective flap over and presses it against the outer side of the adjacent major panel. A further stage of processing involves the application of adhesive to the closing flap or lid, i.e., to that flap which is folded over and adhesively secured to the adjacent panel subsequent to introduction of the material to be shipped, stored or mailed into the interior of the envelope.
A drawback of the just described folding apparatus is that they are quite long and bulky. The main reason for bulkiness of conventional folding apparatus is the presence of aforediscussed loop-shaped folding means which causes one of the major panels to overlie the other major panel. Moreover, the blanks are advanced and held exclusively by belts which are incapable of insuring accurate retention of successive blanks in identical positions, i.e., the dimensions of envelopes often deviate from the desired norm. The deviations from norm are especially pronounced when the envelopes are made of lightweight (thin and porous) paper sheet stock.